Telephone system



Nov. 1, 1927. 1,647,796

L. L. GLEZEN ET AL.

TELEPHONE SYSTEM Filed Aug. 6, 1926 3 Sheets-Meet l Lee Z. 6/526)?//7ve/71ars.' JQmz/e/ PJbacK/ehm [award Vruam by t 45% Nov. 1, 1927. v1,647,796

7 L. L. GLEZEN ET AL,

TELEPHONE SYSTEM Filed Aug) 6. 1926 s Sheets-Sheet 2 lnvemars: Samuel 1?Shack/afar) fdIVd/d ram by ZZ A77)? Nov. 1, 1927.

L. I... GLEZEN ET AL.

TELEPHONE SYSTEM 3 Sheets-Sheet 3 Filed Aug. a. 1926 lee L G/ezen We/#0219. Jamue/ f. JbacK/efan Patented Nov. 1, 1927.

UNITED STATES PATENT OFFICE.

LEE L. GLEZEN, 0F MILLBURN, SAMUEL P. SHACKLETON, 0F WYOMING, NEWJERSEY,

AND EDWARD VROOM, OF OSSININ G, NEW YORK; SAID VROOM ASSIGNOR' TO WEST-ERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OFNEW YORK; SAID GLEZEN AND SAID SHACKLETON ASSIGNORS TO AMERICANTELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Application filed August 6, 1926. Serial No. 127,500.

This invention relates to telephone systems, and more particularly tothe automatic selection and insertion of speech amplifying.

type has also heretofore been controlled manually. It is evident thatsuch control may be subject to errors that may affect the transmissioneilicieney.

The invention has been applied to a systein similar to that disclosed inthe copendnecting stations.

arrangement is such that an automatic discrimination is made betweenlines that do not require. theaddition of a repeater and those that dorequire this addition;

According to the present invention a system is provided whereby when arepeater is required a discriminating apparatus functions to start theautomatic selection and conneetion of a repeater and gain controlapparatus between two toll lines.

' It should be understood that this 1'nven tion is not limited in itsuse to theparticular system employed to illustratetlns application inpractice, but may readily be used 1n any systems in which two linesrequire the addition of a repeater.

The invention contemplates the use of a selecting mechanism associatedwith each of a plurality of cord circuits. These selectors are adaptedto automatically hunt for and connect the cord circuit with an idlerepeater equipment, a plurality of which are provided for the common useof said cord circuits. "When acord circuit has been connected betweentwo toll lines requiringa repeater and the associated selector has foundan idle repeater this repeater is immediately made busy to all otherrepeater selectors. There is also provided a lock-out arrangementwhereby only one repeater selector at a time ]S permitted to hunt for'anidle repeater. Each repeater is equipped with two line finder switchesso arranged that as soon as a repeater has been engaged by a cordcircuit one of the corresponding line finders begins to hunt for one ofthe toll lines connected with the cord circuit and when this toll linehas been found the other line finder begins to hunt for the other tollline connected with the cord circuit. Assoon as the two toll linesare'found by the respective line finders the lines are made busy toother line finders, associated with other repeaters, that later maybegin hunting for engaged toll lines. \Vhen all of these selections forinserting a repeater between two toll lines are completed the lock-outarrangement is actuated to permit repeater selection by another cordclrcuit to take place.

When a. call is completed over a connection of this type between twotoll lines, the repeater selector used is not actuated to return to anynormal position, but remains with its brushes on the terminals of therepeater last employed, whereas the associated line finders are returnedto normal.

In the above mentioned system .employed to illustrate this invention,means is also provided for adjusting the gain control apparatusassociated with each repeater to the net gain required by the two tolllines connected with a repeater. The function of this adjusting means isautomatic and controlled by certain transmission equalizing resistancesassociated with each line requiring a repeater.

Referring now to the drawings, Fig. 1 illustrates the incoming end of atoll line re quiring a repeater and terminating in a jack and in theterminal bank of a line finder arranged to hunt over this bank. Fig. 2illustrates the incoming end of a toll line thatdoes not require arepeater. Fig. 3 shows a cord circuit equipped for use with either ofthe above types of toll lines and is provided with a selector switchwhereby an idle repeater may be selected. This figure also shows one ofthe repeaters suitable for insertion between the toll lines. Fig. 4shows the incoming end of'another toll line requiring a repeaterterminating in a jack and in the terminal bank of another line finderarranged to hunt over this bank. The l ne finders in Figs. 1 and 4 areassociated with the repeater equipment shown in Fig. 3. Fig. 5-illustrates the incoming end of another toll line that does not requirea repeater.

In general the apparatus and functions of the systems shown are asfollows: Assuming, for example, that the line A in Fig. 1 and the line Bin Fig. 4 are to be interconnected. As these lines require the additionof a repeater for speech amplification, they are equipped with specialdiscriminating resistanee units in the sleeve circuits of the re-.

spective jacks 5 and 6, so that when the plugs T and 8 of the cordcircult C shown in Fig. 3 are inserted, respectively, in 1acks 5 and '6,certain functions'are effected in the cord circuit resulting in theselection and intertion of a repeater such as E between these two lines.The first efiect in-t-he cord circuit is that the repeater selector Dstarts to hunt for an idle repeater. This selector may be of any wellknown type of rotary stepby-step switches having a stepping magnet and aseries of brushes actuated thereby to travel over circular terminalbanks. One of the repeaters indicated with the letter E has been shownassociated with the terminals of the five banks of the selector D. Itshould be understood that a plurality of repeaters such as E areassociated with the terminal banks of the selector D, and are connectedin multiple to corresponding terminal banks of other repeater selectorsindividual to other cord circuits.

When an idle repeater such as E has been found it is immediately madebusy to other repeater selectors. Also, all the cord circuits and theirassociated repeater selectors are so arranged in a common lock-outcircuit arrangement, indicated at F, that only one repeater selector atthe time can hunt for an idle repeater. lVhen the repeater selector Dfinds an idle repeater such as E, circuit operations areimmediatelyinitiated to start the line finder G to hunt for the line A,a hunting terminal of this line A having been marked at the time theselector D started to hunt for a repeater. The line finder G is arrangedto stop its brushes on the terminals of the line A when found. lVhen theconnection of line A through the line finder G is completedthrough tothe repeater E, circuit changes will take place to start the line finderT of the repeater E to hunt for the line B. As the corresponding huntingterminal of this line is marked at the same time as the hunting terminalof line A is marked, line finder H will stop on the terminals of theline B when found. The line finders G and H may be of any well knownpanel type construction in which a Set of brushes are moved by theactuation of an up and a down magnet over a vertical bank of terminalsand in which the control of the finders is regulated by a set of brushestraveling over a series of commutator segments. At this time, that is,when the lines A and B are connected through the repeater E, thelock-out arrangement F operates to permit another cord circuit and itsassociated repeater selector to function to select an idle repeater. Itshould be noted that the line finders G and H also connect balancingnetworks N and N through the repeater E to the lines A and B,respectively. These lines A and B are also arranged with certainresistance values of the winding; of relays 10 and 11, these valuesdepending upon the transmission equivalents of the lines. Associatedwith the repeater E are gain control units 12 and 13 illustrated merelyby boxes. These gain control units may consist, as is well known in theart of combinations of marginal relays that may be operated in dilferentcombinations when battery through the windings l0 and 11 is connectedthereto. The operation of such different combinations of relays mayaffect various impedance elements in the units to adjust the gain of therepeater. Thus, each toll line, according to the particular value of itsassociated resistance adjusts the gain of the repeater to the net gainrequired by the transmission characteristics of the corresponding line.

To bring out more fully the features of this invention detaileddescriptions will now be made of the two types of connections' that maybe established by means of cord circuit C. If a connection is desiredbetween two toll lines requiring a repeater in serted between them, thefirst action on the part ofthe toll operator, after she has receivedindications through the usual indicating lamp (not shown) that aconnection is desired over line A, is to insert plug 7 into jack 5 andto operate the talking key 112 to connect her telephone set (not shown)to the talking conductors of the cord C and line A. As the means forcalling the toll operators attention to toll line A does not form partof this invention and as any well known means may be employed therefor,it has not been illustrated. The toll opera.- tor may now communicatewith the operator at the distant end of line A and receive the number ofthe wanted subscribers line. As it was assumed that a repeater wasrequired in this connection, it may be extended over toll line B to adistant station where the connection may be completed in any well knownmanner to the wanted sul scribers line. The toll operator will,therefore, restore her talking key 112 after receiving the desiredinformation, and insert plug 8 into jack 6 of toll line B.

llh

repeater in the connection as follows: On the insertion of plugs 7 and 8into jacks 5 and 6, respectivel the following circuits are completed. necircuit for the operations of relays 21, 22, 23 and 24 may be traced asfollows: battery, winding of relay 21, left hand winding of relay .22,armature and back contact of relay 25, tip terminals of plug 7 and jack5, windings of relays 23 and 24 in series to ground. Due to thecomparatively low resistance of the windings of relays 23 and 24, relay21 operates in ser es with relay 22, the operation of relay 211ndicating that the cord circuit is connected to a line requiring theinsertion of a repeater. A similar circuit is prepared for the operationof relays 26, 27, 28 and 29. This circuit may be traced from batterythrough the winding of relay 26, make-before-break contacts of relay 30,right hand winding of relay 27, right hand armature and back contact ofrelay 30, sleeve terminals of plug 8 and jack 6, windings of relay 28and 29 to ground. The operation of relay 26 1n this instance indicatesthat toll line B is one requiring the insertion of a repeater. Theoperation of relays 22 and 27 causes the operation of relay 31 over thefollowing circuit: battery, Winding of relay 31, armatures and backcontacts of ringing relays 33 and 34 to the left hand armature and frontcontact of relay 22 to ground and left hand inner armature and frontcontact of relay 27 to ground. It will be noted that these lastmentioned connections to ground also provide a circuit for relay 32through the armature and back contact of relay 31, but as relay 31 isfaster in its operation than relay 32, this latter relay will notoperate and, consequently, not close a connection for relay 35 thatwould cause the lightm of lamp 36. The circumstances under w 'ich lamp36 became lighted will be explained later.

Provided the look-out arrangement indicated at F is not in use byanother cord circuit at this time the ground connection due to theoperation of relays 21 and 26 WlllIlQW cause the operation of relay 39over a circuit as follows: battery, make-before-break contacts of relay39 and the correspondin contacts of other similar relays individua -toother cord circuits, such as relays 41 and 42 in the lock-out circuit,through the right hand winding of relay 39, inner right hand armatureand front contact of relay 21 and inner left hand armature and frontcontact of relay 26 to ground. The operation of relay 39 opens theconnection to battery through its make-before-break contacts for theother relays in the look-out circuit and thus prevents any other cordcircuit from functioning to select the repeater. In other words, onlyone of the lock-out relays may -be operated at a time and when a relayonce release of relay 24 causes a connection to ground to be made forthe hunting terminal 43 of line finder G and the release of relay 29causes a ground to be connected to a hunting terminal 45 of line finderH. The

terminals of lines A and B in the terminal banks of line finders G and Hare thereby marked for hunting. On the operationof relay 30, relay 26 isreleased and a connection for the maintenance of relays 27 and 28operated is noW extended through the left hand armature and frontcontact of relay 30. The ground for the operation of relays 25 and 30also causesv the operation of relay 4? as follows: battery, winding ofrelay 47, right handarmature and front contact of relay 39 to ground.Relay 47 in operating provides a locking circuit for itself through itsleft hand armature and front contact, through the right hand armatureand front contact of relay 22 and outer left hand armature and backcontact of relay 27 to ground. The operation of relay 47 closes acircuit for the stepping magnet 50 for the starting of the repeaterselector D, provided the brushes thereof do not rest on the terminals ofan idle repeater. If they rest on the terminals of an engaged repeater,a circuit Will be completed for the stepping magnet. 50 as follows:battery, through the winding, armature and back contact of magnet 50,middle right hand armature and front contact of relay 47, winding ofrelay 52, left hand armature and back contact of relay 53, through thebrush of the terminal bank 56, through the connected terminals of thisbank, the corresponding terminal and brush of the repeat-er selectorengaged with a repeater and the ground at the armature and front contactof the relay corresponding to relay 53 in the engaged cord circuit. Inthis case relay 52 will operate as it is faster in its operation thanrelay 53, which, it will be noted, has a circuit completed through theouter right hand armature of relay 47 and and armature and front contactof relay 52. As relay 52 is always slow to release, it will remainoperated'while the magnet 50 will step the brushes of the repeaterselector D until they come in contact with the terminals of an idlerepeater, at which time it will find no ground on the correspondingterminal of bank 56. Relay 52 will now release and permit the operationof relay 53. Relay 53 in loo operating its left hand armature connectingit to ground makes the repeater selector 1) bus and by operating itsright hand arinag turc causes the operation of relay 58 over a contactof re relay 53 and it is suclia groundthat caused particularrepeaterlousy.-

This ground on't'he selected terminal of.

bank 56 nowalso causes the operation of relays-Wand (31 over circuits asfollows: bat-- tour; lower winding-of relay 60,. armature and backcontact of relay.62,'through-bank .36 togrou nd at the leftha'ndarmature and l'ri-iutxcontactof relz'iyhl and from-battery otrelay G5 toground. This relay 60 now relay 62.

through the windingotrelay 61 to' the same ground. I lie-lay (SOinoperating closes a lockingrircuit for itselt to its inner upperarmature and front. contact and upper winding to thefuppcr innerarmature and front contact causes the line tinder-G to function byclosing a circuit for up-dri'ye' magnet 64 as follows: battery,rip-drive magnet 64., .inner, lower armature and 'tront'contact of relay(30, upper outer armatureand back contact of relay 65, commutatorsegment 67 and the cooperating brush of the group 75 as shown to ground.Line tinder brushes 70 will now he moved up over the terminal bankassociated with this line finder G and hunt for the terminals of line A.When the upper brush of group 70 comes in contact with terminal l3 ofline A the ground applied to this terminal causes the operation of therelay (3.) over a circuit as follows: battery, outer lower armature andback contact of relay T2, lower winding of relay 65, upper brush oi thegroup 70, terminal 43, armatures and back contacts of relays 10 and 24,and armature and front contact of relay 23 to ground. As soon as theline finder starts upward to hunt for the line A, a ground is connectedthrough brush group to the commutator segment 76. This ground causes theoperation of relay 77 over a circuit as follows: battery, winding ofrelay 77, commutator segments 76 and the right hand brush of the group75 to ground. Relay 77 in operating closes an obvious circuit for theoperation of To arrest the upward movement of brushes 70 and 75 at theproper time, the connection from the commutator segment 67 is placedunder control of relay 65, so that when this relay operates the up-drivemagnet- Gl is deenergized. The operation of relay 65 opens the lockingcircuit for relay 60 previously traced through the contact of relay 65.A second locking circuit for relay (S0 is established through-thecommutator segment 79 The momentum of the switchbrush n'iechanismusually carries the-brushes a shortdistan'ceahovethe center of the ter-"ln'inals on whiclrthey are intended to be brought to rest.- (hen thebrushes have overthrown in this manner the commutator brushisassociated-witlr-a conducting seg-' nientof commutator 79. During thetime that theeonnnnt'atorhrush is associated with v I this conductingportion of commutator 79, stepping ma nate to operate and make tins theaforementioned locking circuit is-established for relay (i0. Relaytit)will thereforeamanner well knoWn-in-the art. When'the brushes have beenproperly centered the left insulated portion of'segment 79 so'that relay'60 releases. This relay in releasing causes.

the operation of relay 80 over a circuit as follows: battery, winding ofrelay 80, upper arniaturefand .t'ront. contact-of relay "FT, upper.outer armature andback contact of relay 60, commutator segment 76 toground.

Relay 80 n operating causes the operation of relay 10 over a circuit asfollows: battery, winding of relay 1O, terminal 81 and the associatedbrush of the group 70, lower armature and frontcontact of relay 80 tothe automatic gain control circuit 12, where this circuit may find aconnection to ground through a series of marginal relays. Ashereinbefore mentioned, any well known type of gain control circuit maybe used and it is evident that the particular resistance value of thewinding of relay 10 will cause proper adjustment of the gain controlcircuit 12 to suit the requirements of the line A. As the gain controlcircuit itself does not form a part of this invention, no description ofits operation will be made. Gain control circuits such as are disclosedin the copending application of H. 'J. Fisher, Serial No. 95,582, filedMarch 18, 1926 are of the type that may be adaptedfor use in therepeater employed in this circuit. The only change that would have to bemade is that the relays for controlling the gain would be marginal andconnected to the control circuit established by the operation ofrelay-80. The operation of relay 10 removes the ground from the huntingterminal 43, thus making the line A busy to other line finders. The lineA and the network N are now associated with one side of the repeaterselected through the terminals 82 and 83 and the corresponding brushesof group 70.

hand hrush'of the groupJYS isresting on an v e5 ion vides a lockingcircuit for itself through its upper inner armature, front contact anupper winding to the upper inner armature and back contact of relay 94.The operation of relay 90 starts the line finder H to hunt for the tollline B and the operations of this line finder are similar to theoperation of line finder G. That is, on the operation of relay 90 thetip-magnet 95 of'this line finder will be energized over a circuit thatreceives ground from the commutator segment 96. As the brushes 97 movefrom normal over the commutator a circuit is completed for the operationof relay 98 from ground and segment 140. The operation of relay 98causes the operation of relay 91 and the operation of relay 91 opens theoriginal energizing circuit for relay 90 which, however, is not releaseduntil the brushes 100 of line finder 1 are centered on the terminals ofline B. The operation of relay 94 opens the energizing circuit forup-drive magnet 95 to arrest the upward movement of the switch brushes.The operation of relay 94 also opens one holding circuit for relay 90.When the switch brushes are properly centered the holding circuitthrough the centering commutator for relay 90 is opened and this relayreleases. The'brushes 100 of line finder H are now, therefore, centeredon the terminals of line B and this line and the associated network Nare associated with the opposite end of repeater E. On the release ofrelay 90, relay 101 operates to close a connection for the o eration ofrelay 11 and the adjustment of the gain control circuit 13 in the samemanner as the operation of relay 10 was effected and the gain controlcircuit 12 was adjusted.

The operation of relay 101 completes a circuit to ground at its upperarmature and front contact. This ground is applied to a terminal of bank102 of the repeater selector D through the associated brush to the lefthand armatures of relay 58. The ground applied at the outer left handarmature and front contact of rela 58 short circuits the left handwinding 0 relay 39 so that this relay will not now release and restorethe chain circuit to battery through the corre spending relays such as41 and 42 of other cord circuits, permitting another cord circuit toactuate its repeater selector to hunt for an idle repeater. The releaseof relay 39 does not effect the release of relays 25 and 30 which arenow held up over the circuit completed to ground at the outer left handarmature and front contact of relay 27 through the left hand armatureand front contact of relay 47. The ground applied to the inner left handarmature and front contact of relay 58 causes the operations of therelays 105, 106 and 107, as follows: battery through the windings ofrelays 105, 106 and 107 through the lower closed contacts of armatureand front contact of relay 58. This ground applied at the inner lefthand armature and front contact of relay 58 also causes the operation ofrelay 115 over a circuit as follows: battery, winding of relay 115, aterminal of bank 116 and the associated brush of the selector D, righthand armature and front contact of relay 58, lower closed contacts ofringing key 111, lower closed contacts of ringing key 110, right handarmature and back contact of relay 32, lower closed contacts of talkingkey 112 to the inner left hand armature and front contact of relay 58.The operation of relay 115 closes a circuit for the operation of relays119 and 120 over circuits as follows: battery, windings of relays 119and 120, arma-- ture and front contact of relay 115 to the ground at theupper armature and front contact of relay 101. Relays 105 and 106 inoperating opens the connection between the two toll lines A and Bthrough the cord circuit C and the operation of relay 107 connects themonitoring leads from the operators telephone set to the repeater sothat in case the operator decides to monitor on the connection she maydo so at this time by operating key 20. A circuit for the operatorstelephone set in this instance may be traced as follows: from the setthrough contacts of key 20, upper armature and front contact of relay107, the brush and associated terminal of bank 124, a winding of hybridcoil 125, a winding of hybrid coil 126, a terminal of bank 127 and theassociated brush, lower armature and front contact of relay 107 andlower cont-acts of key 20.

The operation of relays 119 and 120 cause connections from the lines Aand B and networks N and N to be completed to the repeater E. Thecircuit from line A may be traced through terminals 82 and theassociated brushes of line finder G, the upper two armatures and frontcontacts of relay 119, windings of hybrid coil 125, lower armatures andfront contacts of relay 119 to the terminals 83 through the associatedbrushes to network N Similarly, line B is connected through terminals130 and associated brushes of line finder H, upper armatures and frontcontacts of relay 120, winding of hybrid coil 126, lower armatures andfront contacts of relay 120, lower brushes and terminals 131 to thenetwork N The hybrid coil 125 is connected through any well known inputcircuit under control of the gain control circuit 12 to the vacuum tubeamplifier 134, the output circuit of which is connected to anywell'known filter arrangement 136 to windings of hybrid coil 126. Thisconstitutes the circuit for transmission from line A to line B. Thecircuit for transmission from line B to line A is completed from thehybrid coil 126 throu h any well known input circuit controlled y thegain control circuit 13 and connected to the vacuum tube amplifier 137,the output circuit of which is connected to any well known filterarrangement 132 and windings of hybrid coil 125. As the type of repeateris 11nmaterial, as far as this invention is concerned, no furtherdescription of its construction or operation will be made. It should beunderstood that any repeater arrangement well known in the telephone artmay be employed in circuits of this general character. Conversationthrough the repeater E from line A to line B or from line B to line Amay now take place, although, of course, the connection has to beextended from line B at the distant station to the wanted subscriberbefore such conversation can actually take Place.

\Vhen such a connection is completed in any well known manner andconversation between the parties connected through lines A and B isended, the toll operator may receive suitable indications to this effectand to break up the connection she will remove plugs 7 and 8 from jacks5 and 6. This causes the release of relays 23, 28, 22, 21 and 27. Therelease of relays 22 and 27 causes the release of relay 47. The releaseof this relay causes the release of relays 25, 30 and 53. The release ofrelay 53 causes the release of relays 61 and 58 and the release of thislatter relay causes the release of relays 105, 106, 107 and 115. Therelease of relay 115 causes the release of relays 119 and 120. so thatthe repeater E is now disconnected from the lines A and B and the cordcircuit is thereby restored to normal. The release of relay 61 causesthe operation of relays 72 and 135. The circuit of relay 72 may betraced as follows: battery, lower outer armature and back contact ofrelay 60, lower winding of relay 72, armature and front contact of relay(i1, commutator segment 76 to ground. Relay 72 provides a lockingcircuit for itself through its upper armature, front contact and upperwinding to the ground on commutator segment 76 and closes an obviouscircuit for down-magnet 127. hen

the line finder G has returned completely to normal the circuit forrelay 7 2.is opened as the brush associated with commutator segment 76leaves this segment. Relay 72 in releasing, stops the down-magnet 127.Similarly. on the operation of relay 135 a circuit. is completed forthis relay through the comniutator segment 140 and the operation of thisrelay closes an obvious circuit for downmagnet 14:2 for the release ofline finder H to normal. Relay 135 is locked through the commutatorsegment 140 until the line finder is completely returned, when thisrelay is released and the down-magnet 142 is released to step the linefinder in normal position. A'll relays held in an operated positionthrough the agency of commutator segments 76 and 140 are released whenthe brushes and 97 are restored to their normal positions. The cordcircuit C',, repeater tant ends of line A or B is connected to theselines for supervision, a corresponding ringing relay 33 or 34 willoperate to cause the lighting of lamp 36. For example, if relay 33 isoperated, the circuit through the armature and back contact of relay 33is opened. Relay 31 is thereby released to permit the operation of relay32 over a circuit as follows: battery, winding of relay 32, armature andback contact of relay 31, left hand armature and front contact of relay22 to ground. The operation of relay 32 closes an obvious circuit forthe operation of relay 35. Relay 35 locks to ground at the uppercontacts of talking key 112. Re lay 35 in operating closes an obviouscircuit for the lighting of lamp 36. Lamp 36 is extinguished byoperating key 112. It should be noted that when key 112 is operatedrelays 105, 107 and 106 are released so that a talking connection iscompleted from line A to the operators telephone set and on theoperation of relay 32 the circuit for relay 115 is open so that thisrelay in releasing causes the temporary disassociation of the repeaterfrom the line by the release of relays 119 and 120. This prevents therepeater from singing during the ringing interval. The operation of thetalking key 112 will also release relays 115, 11.9 and 120 to eliminatethe repeater during conversation.

If connection is desired between two lines that do not require arepeater, the following operations take place. In this case lines suchas the ones shown in. Figs. 2 and 5 may be used. On the insertion ofplug 7 into jack 150 of line K a circuit is completed from groundthrough the high resistance winding of the supervisory relay 151, sleeveterminals of jack 150 and plug 7, armature and back contact of, relay25, windings of relays 22 and 21 in series to battery. Due to the highresistance of the winding of relay 150, relay 21 does not operates butrelays 150 and 22 do operate in this circuit. Relay 150 performs theusual supervisory functions in ordinary toll lines, as is well known inthe art. Similarly, on the insertion of plug 8 into jack 155 of line L,a circuit is closed for the operation of relay 27 and the relay 157having a high resistance winding. In this circuit relay 26 is not operlion ated. On the operation of relays 22 and 27 a circuit is connectedfor the operation of relay 31 as previously traced. The operation ofthis relay prevents the operation of relay 32, so that lamp 36 is notlighted at this time. The fact that relays 22 and '26 are not operatedat this time prevents the repeater selector D from functioning toinclude a repeater between lines K and L, and the cord circuit is nowcompleted through from line K to line L. Talking connection between thetoll operator and the lines K and L may be established by the operationof talking key 112 and ringing supervision of either of those lines maybe established in the same manner as hereinbefore described by thelighting of lamp 36.

Vthat is claimed is: I

1. In a telephone system, lines, repeater equipments, means whereby anytwo ofsaid lines may be interconnected, selecting apparatus, and meansautomatically operable in response to the interconnection of two of saidlines to select an idle repeater equipment and interpolate said repeaterequipment between said two lines.

' 2. In a telephone system, lines, repeater equipments, means wherebyany two of said lines may be interconnected, switching apparatus forselecting an idle repeater equipment, other switching apparatus forinterpolating a selected idle repeater equipment between twointerconnected lines, and means automatically responsive to theinterconnection of two of said lines for actuating said switchingapparatus.

3.1m a telephone system, lines, repeater equipments, a cord circuit forinterconnecting any two of said lines, selecting apparatus, and meansautomatically operable in response to the interconnection of two of saidlines to select an idle repeater equipment and interpolate said repeaterequipment between said two lines.

4. In a telephone system, lines, repeater equipments, a cord circuit forinterconnecting two of said lines, means in said cord circuit for theselection of an idle repeater equipment, and means operative upon theselection of a repeater equipment to connect each of said interconnectedlines to the repeater equipment and to open the connection between saidcord circuit and said lines.

5. In a telephone system, lines, repeater equipments, a cord circuit forinterconnectin two of said lines, means in sai-dcord circuit for theselection of an idle repeater equipment, automatic switching meansassociated with each of said. repeater equipments for finding andcomiecting lines to the corresponding repeater equipment, and means forstarting the operation of an automatic switching means responsive to theselection of the associated repeater equipment by said cord circuit tofind and connect each of said interconnected lines with said repeaterequipment.

6. In a telephone system, lines, repeater equipments, a cord circuit, aswitch associated with said, cord circuit for selecting an idle repeaterequipment, two switches associated with each repeater equipment forselecting lines, means responsive to the connection of the cord circuitbetween two of said lines for actuating the first mentioned switch tohunt for an idle repeater equipment. and means responsive to the findingof an idle repeater equipment for actuating the associated switches tohunt for the two lines associated with the cord circuit and connect theselected repeater equipment between them.

7. In a telephone system, lines, repeater equipments, a cord circuit, aswitch associated with said cord circuit for selecting an idle repeaterequipment, two switches associated with each repeater equipment forselecting lines, means responsive to the connection of the cord circuitbetween two of said lines for marking the terminals of said lines on thesaid switches of the repeater equipments and for actuating the firstmentioned switch to hunt for an idle repeater equipment and meansresponsive to the finding of an idle repeater equipment for actuatingthe associated switches to hunt for the marked terminals of said twolines and to connect the selected repeater equipment between saidterminals.

8. In a telephone system, lines, repeater equipments, a plurality ofcord circuits, a switch associated with each cord circuit for selectingan idle repeater equipment, two switches associated with each repeaterequipment, means responsive to the connection of a cord circuit with twoof said lines for actuating the switch associated with said cord circuitto select an idle repeater equipment, means for thereafter actuating oneof the switches associated with the selected repeater equipment to findone of the lines associated with the cord circuit; means for thereafteractuating the other of said switches associated with the selectedrepeater equipment to find the other of said lines, and means forthereafter connecting said selected repeater equipment between said twolines and for opening the connection established over the cord circuitbetween said two lines.

9. In a telephone system, lines, repeater equipments, a plurality ofautomatic means for connecting an idle repeater equipment between two ofsaid lines, means for initiating the operation of any one of saidautomatic means, and means for preventing more than one of saidautomatic means from completing its function at a time.

10. In a telephone system, lines, repeater equipments, a plurality ofautomatic means for connecting an idle repeater equipment between two ofsaid lines, means for initiating the operation of any one of saidautomatic means, and means responsive to the actuation of any one ofsaid automatic means for delaying the actuation of any one of the otherot the automatic means until said first automatic means has completedits functions.

11. In a telephone system, lines, repeater equipments, a plurality ofcord circuits, 2, switch associated with each cord circuit for selectingan idle repeater equipment, switching means associated with eachrepeater equipment for selectlng lines, means responsive to theconnection of a cord circuit between two of said lines for actuating theswitch associated with said cord circuit to select an idle repeaterequipment, means responsive to the finding of an idle repeater equipmentfor actuating the associated switching means to find the two linesassociated with the cord circuit and connect the selected repeaterequipment therehetween,

and means for preventil'ig the establishing i LEE L. GLEZEN. SAMUEL P.SHAOKLETON. EDWARD VROOM.

